Tunnel breasting jumbo



Aug. W W56 L. n. WKLBUR ETAL TUNNEL BREASTING JUMBO 7 Sheets-Sheet 1Filed Aug. 4, 1952 INVEN TORS 0. am mm IN M. M2; Arm/Wm Aug. R958 L, m.WILBUR ET AL TUNNEL BREASTING JUMBO 7 Sheets-Sheet 2 Filed. Aug. 4, 1952gRR/TT MZQ/l ATTUH/VEV 1956 L. D. WILBUR ETAL TUNNEL BREASTING JUMBO 7Sheets-Sheet 3' Filed Aug. 4, 1952 INVENTORS W! L HUI? MERE/7'7 M. MASONBY, w

LYMAN 0. )6 h 8.? 9 1956 L. D. WILBUR ETAL TUNNEL BREASTING JUMBO 7Sheets-Sheet 4 INVENTORS LYMA/V D. W/LBUH Filed Aug. 4. 1952 A 7' TORNEYII... D. WHLBUR ETAXW TUNNEL BREASTING JUMBO 7 Shee'hsSheet 7 Filed Aug.4, 1952 mw wm d wmw mm TUNNEL BREASTING J UMBO Lyman Dwight Wilbur,Boise, Idaho, and Merritt M. Mason, Richmond, Calif; said Mason assignorto Noble (3b., 'Uairiand, Calif, a corporation of California ApplicationAugust 4, 1952, Serial No. 302,550

8 Claims. (Cl. 61-85) This invention relates to improvements in ahydraulic breast boarding jumbo for use in tunnel excavation.

The invention is primarily useful in ground too heavy and rocky for ashield and not solid enough to be stable without external support. Theproblem in this type of situation is to support the face of the core tobe removed against caving while installing permanent steel supports andblocking, prior to pouring the usual concrete lining of the tunnel.

Heretofore it has been necessary to work slowly when removing the corein this type of a bore. One method in a large tunnel has been to make aplurality of passes through the tunnel removing only a small part of thecore at a time. This was costly and time consuming because of the needfor careful blocking of the roof over each core; the need for handremoval of excavated material to a point where machine carrying can pickit up; and because of the difficulty of placing the permanent steelsupports for the roof of the tunnel.

The invention solves this problem by allowing miners to release theforwardly applied support from small areas and to remove the dirt inthat small area, while maintaining the support on the balance of thecore face. Then it permits extending the support into the smallexcavated area. This small area excavation is repeated for each of theforward supporting means. The plurality of forward pressure applyingmeans are rams mounted on a movable car and the invention allows thewhole car or jumbo structure to be moved forward without releasingpressure from the forwardly extended rams. Thus, when the forward ramshave reached their maximum extended position, the car or jumbo on whichthe ram cylinders are carried can be moved forward by oppositelyextending rams while still maintaining adequate pressure on the forwardrams as they are forcibly pushed back into their respective retractedpositions. From this point on, the operation is repetitive untiltheminers have again removed sumcient of the core from in front of each ofthe individual rams and installed overhead permanent steel supports inthe advanced position.

Another problem solved by this structure relates to the placement of thepermanent steel ribs or supports for the tunnel. With this device theribs can be hoisted onto cars operating on rails extending along theentire length of the jumbo. On these cars the ribs are carried to theface of the bore and lifted into final position by means ofhydraulically operated devices permanently installed on the cars. Priorto the development of this machine, the time required to place a set ofsteel ribs was about two hours. After use of this machine was begun, theoperation of placing a set of steel ribs was reduced to 15 to 20minutes. This is just one place in which time and labor has been cut bythe invention.

Another important problem solved by the invention is in providing aseries of working platforms for the miners as the core removalprogresses. Heretofore timbers and scaffold had to be built for thispurpose; whereas with the extension of the supporting rams on the frontof the States Patent F 2,757,515 Patented Aug. 7, 1956 r ll jumbo, aperfect support for the miners can be provided at each digging levelsimply by laying planks across these extended rams.

Where the height of the tunnel is sufiicient to permit the use of a coresupporting structure high in the bore, it is possible to use under thejumbo a mucking machine for removal of the broken material as it isremoved from the face of the core.

Another advantage of the invention is that it has made possible speedingup the mining operation by the use of light shots of explosive to loosenmaterial in the core. On the particular tunnel on which this inventionwas first used, the soft nature of the materials had made it exceedinglydangerous theretofore to use any explosive to speed up the work becauseit was impossible to control the caving and settlement of the groundabove.

With the present invention the individual rams maintained a support onthe face of the tunnel while these shots were exploded, thus preventingundue caving. The jacks held the loosened material until the miners wereready to remove it.

All of the foregoing advantages, plus the fact that the miners feel safeand have a nice place in which to work, has meant that the firsttunneling operation on which the invention was used was speeded upapproximately 400 percent. Whereas the bore was progressing at about 4feet a day it increased to about 16 feet a day when the machine wasplaced in use.

Another advantage of the invention is the provision of means formechanically locking all the rams in a position to maintain pressure onthe face of the core independently of maintenance of hydraulic pressurein the rams, thus removing dangers incident to a shut down from a powerfailure, holidays, or from any other causes. The machine can be leftindefinitely in a bore without any attendants as it would be in case ofa strike.

It is therefore the object of this invention to provide a tunnelbreasting jumbo having a plurality of individual forwardly extendingpressure applying rams; to provide a movable unitary support for saidrams; to provide a control system for said rams so they can be extendedindividually as the loosened core under each is removed; to provide acontrol system for said rams so they can be yieldably supported tomaintain a predetermined sup porting force against the core face whilethe movable support is moved toward the core face thereby forcing saidrams into their retracted position ready for another cycle of coreremoval; to provide a control system for said rams so each will moveinwardly whenever the forward pressure medium is released; to providemeans for positively locking said rams in any desired positionindependently of the maintenance of hydraulic pressure on the rams; toprovide a support for each ram so that when extended it can serve as ahorizontal support for floor planks for the miners as they loosen thecore ahead of the rams; and to provide cars with lifting means atop thejumbo mounted on tracks running parallel with the tunnel bore and havingextensible track means capable of projecting forwardly out over theextended pressure applying rams for lifting into place the permanentsteel support Where the core has just been removed and of projectingrearwardly out over the rear end of the jumbo for receiving from thetunnel floor the steel support preparatory to carrying it forward on thejumbo for placement.

In summary, What the invention includes is a large unitary movablesupport means A, with a ram housing unit B having a plurality ofindividually movable forwardly extending pressure applying rams B on itsfront end, with a fluid pressure producing means C and a control systemD for the rams on a platform usually amidship, with two or moreindividually movable rearwardly extending pressure applying rams E oneach side for advancing the jumbo forwardly in the bore, and with cars Fmovable fore and aft along the top of the support A.

While, for the purpose of compliance with the Statute, the invention isshown in a'form proven to be practicable, it is not intended hereby tolimit the invention to embodiment in this one form, except as may berequired by the language of the appended Claims. Each element comprisingthe combination is capable of variation to express the choice ofdifferent engineers and some variation may be dictated by'the size ofthe tunnel in which it is to be used.

Reference will now be had to the illustrative embodiment called for byU. 8. Revised Statute 4888 and shown in the drawings which are mainlydiagrammatic and in which Fig. l is a vertical longitudinalcross-sectional view of a tunnel bore taken on a 'line just inside thesteel supporting beams on the side wall and showing in verticalelevation the tunnel jumbo with the forwardly extending pressure ramspartly extended, and the beam carrying car carrying a steel beam towardthe forward end of the jumbo;

Fig. 2 is a horizontal longitudinal cross-sectional view of a tunnelbore as if the top of the here were lifted off at about the line IIII-inFig. 3, leaving the jumbo exposed in plan view;

'Fig. 3 is a cross-sectional view of the upper portion of the tunnelbore taken about on the line Illlll in 1, showing the frame in which theforwardly and rearwardly extending pressure rams are mounted on thefront end of the jumbo;

Fig. 4 'isa view in plan of one of the forwardly extending pressure ramswith the mechanical locking means in place as it would 'be if the jumbowere left unattended;

Fig. 5 is a cross-section view in vertical elevation showing the rampartially extended and the protective housing around it whichalso-serves as the arms for the scaffold to support the miners whiledigging;

Fig. 6 is a view in vertical elevation of the device of Fig. 4 showingthe sockets to receive the mechanical locking means;

Fig. 7 is a view in cross section taken on the line VII--VII of Fig. -6;

Fig. 8 is a view in end elevation of the tote car showing the severaltracks and the frame of the cantilever car in cross section;

Fig. 9 is a planview of the tote car showing it on the cantilever car;and

Fig. 10 is a diagrammatic layout of the control system for the pressureapplying rams.

Referring now to the drawings the several units will be described inorder.

The movable support means A The movable support means A is shown best inFigs. 1 and 2 and comprises the frame or support for all the parts whichtogether constitute thetunnel breasting jumbo.

The support means itself is made up of a braced framework having thelongitudinal members 10, 11 secured together by vertical upright members12 and diagonal braces 13 with lateral bracing and floor supportingbeams (not shown). Near its four corners are the legs 14 each having awheel truck 15 secured at its lower end with flanged wheels 16 engagingthe track rail 17 laid along each edge of the tunnel bore. The front ofthe support means has a vertical frame 18 with braces 19 to provide theanchor plate for the forwardly extending pressure applying jackassembly'B.

On top of the longitudinal members 11 are secured suitable floor joists20 which in turn support a top flooring 21 and the rails 22 for thecantilever cars F. There are two such cars therefore ,four rails 22, asshown in Fig. 2. The rails 22 terminate at the front end of the frame B.

On the lower .of the longitudinal members 16 are secured floor joists(notashown which suport a floor for the 4 hydraulic power unit C, thecontrol section D, and other miscellaneous equipment.

The ram housing Unit B This assembly is preferably made up as a separateunit and is hung on the front end of the support frame A, where it isbolted in place. The forwardly and rearwardly extending rams arepreferably secured to this assembly so it can be made as rugged asneeded Without being dependent on the support frame A for strength.

The ram housing unit B has provision for as many rams as the particulartunnel job requires. The one on which this invention was first used has18 forwardly extending rearwardly extending rams. As shown in Figs. 1,2, and 3, the frame of the ram housing unit B is made up of two sets ofspaced apart horizontal channel members 23 joined together by likevertical members 24. Where each adjacent pair cross they form arectangular space 25 on the vertical inside face of which a fore and aftextending channel 2.6 is secured with its legs facing out. These channels 26 extend between the forward and rear sets of channel members 23,24. Cross braces '27 strengthen the ram housing frame so it can standthe pressures exerted by the rams when-in use. When viewed from thefront, the frame has somewhat the appearance of a honeycomb with therectangular spaces formed between the adjacent flat faces of each pairof channels 26 comprising a cell 28. A plate 2.9 closes the back side'ofeach cell and has legs 30 with a hole 31 adapted to receive a bolt (notshown) by which the ram unit B is secured to the front of the supportmeans A. (See Fig. 4 and broken away portion in Fig. 1.) To add strengthto the ram housing unit in the region where the rearwardly acting ramsexert their force several I beams 33 may be secured.

All of the forward rams are identical and one is shown in detail inFigs. 4 to 7. The housings for the top two rams are pivoted at 34 to theframe B and are adjustably supported at 35 in the extensions 36. Thehousings are like the rigid ones which will now be described and whichwere referred to earlier as the cells 28.

The sliding ram housings 37 In each cell 28 is slidably mounted asliding ram housing 37 which has several important functions. Itprovides for the ram rod 38 and ram cylinder 39 a protection from injuryby .grit, .or boulders which are ever present. It provides a horizontalsupport 40 right at the work zone on which the miners can placetemporary flooring 41, and the guide plates 42 and 43 extending out overthe side channels 26 keep all strain from being put on the ram rod 38,as the plates support the back end of the sliding ram housing and .itsforward end is supported on the lower channel 23 of the cell opening 28.It also provides a member having a plurality of bayonet openings 44 toreceive the lug 45 on the jack flange 46 for the mechanical lookingscrew jack 47 with its tightening nut 48. It also provides a ruggedmounting for the toggle fitting 49 by which the pressure plate 50 issecured to the ram. The inside end 51 of the toggle fitting is pinned at52 to the end of the ram rod 38. The ram cylinder is pinned at 53 toafiange 54 on .the back plate 2? of each cell 28. The ram cylinder hasan inlet 55 at one end and an inlet 56 at the other end so the piston 57can be moved in either direction. .A suitable packing is provided aroundthe .ram rod 38 at the end 3% of the cylinder.

Another functionperformed by the sliding ram housing 37 is in providinga stop to limit its outward movement. This is performed in the devicedescribed by the plate 42 whose edge 58 will engage the upper framemember 23 when the full ram stroke is reached.

As shown in Fig. 7, the sliding ram housing 37 is made up of twochannels 59, .60 with the longitudinally extending plates 61, 62 weldedto the channel legs to form a rectangular box-like housing. Its innerend at 63 is open and its outer end is closed by the plate 64.

The advancing and holding rams E The functions performed by these rams,of which there are preferably two on each side of the machine, areseveral. They provide the backing up or holding support needed for theram housing unit B with the individual forwardly extending rams as thecore removal goes on. They must have a capacity so that when all theforward rams have been extended as the core is removed from in front ofeach ram, they can advance the whole jumbo forward on its tracks 17 andcause the forward rams 37 (which are still supporting the core) to bepushed back into their respective cylinders without letting up on thecore supporting pressure. The hydraulic system for the forward rams hasa relief valve set at a lower pressure than the pressure in theadvancing rams E so that when the push from the latter exceeds therelief valve setting, the hydraulic fluid will be forced out from behindeach piston 57 and the jumbo will move up to the core to start anothercore removal cycle. By having at least a pair of the advancing andholding rams E on each side of the jumbo, the load can be taken by oneram while the other is drawn in and takes a new purchase on the Whalers65 supported along the steel ribs 66 of the tunnel.

As shown in Figs. 1 and 2, the upper rams 67 of the advancing andholding rains E are pivotally secured at 63, while the lower rams 69 aresimilarly secured at 70 both to the back side of the ram housing unit B.Brackets '71 and 72 extend outwardly from the forward legs 14 on theframe A to support the ram E in a generally horizontal position. Theserams differ from those previously described in that here the cylinder ispivoted to the support and the ram rod 73 has a blunt nose 74 whichengages directly with the whaler 65'. A boot 75 keeps dirt from the ramrod. Fluid pressure is introduced either at 76 or 77 in each cylinder. Aworking platform 97 is provided for the operator working with theserams.

The rate and cantilever track cars F One of the time saving advantagesfrom this invention arises from the provision for picking up sections ofthe steel crown rib 73 at the back end of the jumbo and being able tocarry it beyond the forward end of the jumbo (Where the support rams 3'7are holding the core until the crown rib can be put into place), andthen lifting the crown rib into place. On a jumbo of the size shown, itis preferable to have twin tote cars 79 and that necessitates acantilever track car 00 for each. They are identical in constructionexcept that when set on their tracks one has its jack set opposite tothe other. Only one will be described in reference especially to Figs. 8and 9.

The tote cars 79 These cars have a frame 81 supported on four flangedwheels 82 journaled along the side of frame 81 and adapted to run on theflanged cantilever track 83 on the cantilever car 50. A lifting arm 34has a suitable crown rib support 855 at one end and it is pivoted at itsother end 86 to the side frame member 87. The arm 84 is lifted andlowered by the hydraulic jack 88 pivoted at 89 to the arm and at 90 tothe other side frame member. The tote cars are moved along thecantilever tracks 83 by the workman as they roll easily even when thecrown rib is being carried by the two tote cars.

The cantilever cars 80 These cars provide an extended cantilever track83 for the tote cars when at the core end of the jumbo and preferablywhen at the rear end of the jumbo, because the track 22 terminates atthe rear end of the main support frame A and extends only to the forwardend of the frame B. With the cantilever track 83, the tote car can bewheeled up close enough to the core that the crown rib can be liftedinto place with a minimum of physical exertion by the operators.

The cantilever car 80 has a frame 91, 92 with the flanged wheels 93journaled therein at a gauge to fit the rails 22 secured along the topof the jumbo support frames A and B. The upper frame 92 extends beyondeach of the cross members 94 and on its inside has the rails orcantilever track 83 on which the tote car runs. The length of thecantilever track is determined by the distance the tote car has totravel beyond the end of the rails 22 to receive the crown rib from thehoist, and at the other end to carry the crown rib into position at theroof of the bore. The under side of the cantilever car frame 92 has neareach end a cross member 95 with arms 96 and pads 97a which extend underthe flange of each rail 22 so that when the tote car runs out on therails 03 the arms 96 will support the rails in a substantiallyhorizontal position.

The cantilever cars may be moved along the rails 22 by manpower or bymotor power.

The control system From the foregoing description it should be clearthat the core supporting rams 39 and the advancing and holding rams 67,69 must be controlled in a particular relationship in order to gain theadvantages possible with this invention. Reviewed briefly, thisrelationship calls for the following:

1. Controls on the hydraulic circuit to each of the sup porting rams 39so each can be moved independently by hydraulic pressure in eitherdirection;

2. A control on the hydraulic circuit to the supporting rams 39 whichwill permit the rams to be pushed back into their cells 28 while theyretain their full supporting pressure on the core face, as the advancingrams 6'7, 69 move the jumbo toward the core face; and

3. Controls for moving the advancing rams 67, 69.

One form which such controls might take is shown diagrammatically inFig. 10 where for the purpose of clarity only four core supporting rams39 are shown and only two of the advancing rams 67, 69 are shown. Also,only one control valve circuit is shown to one ram 39 and one controlvalve circuit to one advancing ram 67. These are suflicient to give aclear idea of how the complete device is controlled.

The low pressure system This system operates at about 150# pressure andis continuouslyconnected to the fitting 56 on the ram end of eachsupporting ram 39 and the fitting 77 on each advancing ram 67, 69, sothese rams are floating on the line. The only control is the reliefvalve 109 set at about 175# and located between the low pressuremanifold 101 and the return line 102 which brings the oil back to thereservoir 103. The low pressure oil system is kept supplied by the line104 which bleeds off the high pres sure line 105 through the pressureregulator 106. In the control system the low pressure maintained on theram end of each ram 39, 67, 69 effects an inward movement of the ramwhenever its control valve 107, 101i is placed in its open position sothe high pressure fluid is disconnected from the piston end 55, 76 ofthe ram and the fluid in the ram is released so it flows through pipe109, back to the oil reservoir 103. This means great simplificationbecause no separate control valve is needed to return each ram inwardly.The low pressure fluid is always there waiting to act when the operatorplaces either lever 107a or 108a in the open position for the valve 107or 108.

The high pressure system This system operates preferably at about 1200#pressure and is supplied from suitable compressors 111, 112 andreservoir 103 with accumulators 113,. 114, 115 to make up for any leaksand to absorb any shocks in the line 105. Suitable check valves 116 andneedle valves 117 are provided where needed. The high pressure mani fold105 leads to the fitting 55 on the piston end of each supporting ram 39,with a valve 107 interposed between the manifold 105 and each ram 39.Only one of these valves is shown in Fig. 10. In each pipe 118 betweeneach valve 107 and each ram 39 is a relief valve 119 set at about 700#pressure, with its outlet 120 connected back to the reservoir 103. Thehigh pressure line 105 also leads to the fitting 76 on the piston end ofeach advancing ram 67, 69, with a valve 108 interposed between themanifold 105 and each ram 67, 69. There is no relief valve in theselines 121 to the rams 67, 69 because it is necessary to introducesuflicient fluid pressure in these rams to move the whole jumbo towardthe core face against the resistance of the 700$; pressure in thesupporting rams 39.

The valves 107, 108 each have a lever 107a, 108a respectively inconvenient reach of the operator on the con trol panel D, so the valvecan be moved into either of its three positions. In the up position thevalve 107 connects the high pressure manifold 105 with the line 118leading to the piston end of the ram 39. It is in this position that theoperator places the valve when the miners have completed the coreremoval in the area ahead of a particular supporting ram 39. This causesthe ram to move forward against the new core face, simultaneouslyemptying fluid from the ram side of the ram cylinder through the reliefvalve 100 set at 17'5#. The operator may leave the valve 107 in thisposition until it is time to advance the jumbo toward the core face,when it is preferable to move it to its middle position.

In the middle position (full line in Fig. 10), the valve closes theconnection between the :high pressure manifold 105 and the ram 39. Thisleaves the ram 39 still under pressure at or near the pressure in themanifold 105, but no longer connected to the manifold. When the jumbo isadvanced by the rams 67, 69, the pressure fluid escapes from the reliefvalves 119 at about 700.# pressure, thus maintaining a full supportingpressure on the core face as the rams 38 are pushed back into theircylinders 39. The better practice is not to advance the jumbo so closeto the core face that the supporting rams are pushed completely to thebottoms of their respective cylinders.

The down position of the valve 107 closes off the high pressure manifold105 from the ram inlet 55 and connects the piston end of the ram withthe fluid return line 109 in which there is no pressure to speak of.This allows the pressure fluid (about 150#) acting on the ram end of theram 38 to move the ram into its full depth in the cylinder 39, therebywithdrawing the ram supporting face 50 from the cor face directly beforeit, so the miners can remove the core in that localarea. As soon as thecore in that area is removed for a depth at which the extended ram 38will be able to reach conveniently, the miners get out of the way andthe operator moves the valve lever 107a into its upper position. Thisputs the high vpressure on the piston side of the ram which moves theram 38 outwardly against the resistance of the 1504i pressure on the ramside of the cylinder. This latter fluid escapes through the relief valve100 and gives the ram 38 a smooth deliberate stroke as it moves towardand into contact with the new core face. The operator manipulates thevalves 107 oneat a time until the.. I iners out front have removed the.core face around each supporting ram face 50.

A valve 108 is provided for controlling each advancing ram 67, 69 andthis valve is similar to the ones just described. When the jumbo isready to be advanced, the operator actuates the valves 108 to introducethe high pressure fluid medium to the piston end 76 of the rams 67, 69.When the jumbo'has moved forward, as explained above, these rams 67,69stilli'have a holding function to perform so sufiicient pressure is keptin at least one ram 67, 69 on each side to resist the thrust ofthesupporting rams 39 Which-if not resisted-will push the jumbo back awayfrom the core-face. The operator needs to prepare the advancingrams;.67, 69,forthe ne xt forward movement of the jumbo and he does thison one ram at a time by moving its valve handle 108a into its lowerposition where the high pressure fluid is cut off and the low pressurefluid on the ram side of the cylinder 67, 69 moves the ram 73 into thecylinder. The operator places the end 74 of the ram against the nearestWhaler 65 and then actuates the valve 108 to introduce enough pressureon the ram 67, 69 to bring it into holding strength, but not so muchpressure as to overcome the supporting rams 39 and advance the urnboprematurely.

Globe valves 123 may be provided to close the fluid lines to each ram,but they play no part in the normal operating cycle above described.

Any suitable method may be used for obtaining an adequate source offluid under pressure. In Fig. 10, the pump 111 is a high volume lowpressure pump with an unloader 124 which cuts off this pump when it getsthe fluid up to 500# pressure. The pump 112 is a low volume highpressure pump which maintains about 1200# pressure on the high pressureline. It is equipped with a relief pilot unloader 125 to unload the pumpmotor when the pressure gets up to 1200#. These are well known pieces ofequipment and require no further description.

When it is necessary for the work to stop, whether because of a holiday,a strike, or other reason, the crew puts in place the screw jacks 47(see Fig. 4) on each of the rams 38 and adjacent the rams 67, 69 so thatthere is no fluid pressure being employed to maintain the status quo.This means no attendant need be left on duty which is a substantialeconomy for the contractor.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

We claim:

1. In a tunnel breasting jumbo for supporting the core face duringboring of a tunnel the combination of a frame movable horizontally inrelation to the tunnel bore; a plurality of spaced apart forwardlyextending individually extensible and retractable pressure rams securedon the forward end of said frame, adapted to engage the core to beremoved from the tunnel; a plurality of rearwardly extending pressurerams secured to said frame, adapted to engage the walls of said tunnelto hold and to advance said frame horizontally in said tunnel; controlmeans for moving all of said rams selectively in either direction, saidmeans including pressure release mechanism associated with each of theforwardly extended rams and actuated by a rise in fluid pressure whenthe forward movement of said frame is produced by said rearwardlyextending pressure rams, whereby the pressure on the forwardly extendingrams on the core face will be preserved during forward movement of saidjumbo.

said pressure applyingmeans to move each one forward independently ofthe others; return means operative on all of said forward pressureapplying means to move each one backward whenever its forward movementcontrol means is inactivated; a pressure sensitive control on saidforward control means whereby said forward pressure applying means willretain a supporting pressure on the bore as they are pushed into aretracted position as said frame is moved forwardly; and a plurality ofrearward pressure applying means, projecting rearwardly from said frame,and means for energizing said last named means to apply a holding and amoving pressure on said frame.

3. The device of claim 2 it: which each of said forward pressureapplying means includes a ram, a supporting housing surrounding said ramand secured to its forward movable part for movement therewith, and aguide in said frame in which said housing slides.

4. In a tunnel-digging support mechanism, the combination of a frameslidable in a horizontal plane; a plurality of forward pressure-applyingmeans, secured to and projecting forwardly from said frame, each saidmeans comprising a ram having a cylinder, a piston movable therein, anda rod secured to said piston, a supporting housing surrounding said ramand secured to said rod for movement therewith, and a guide in saidframe in which said housing slides; a pressure-sensitive control on saidforward pressure-applying means whereby said forward pressure-applyingmeans will exert a substantially uniform forward pressure while beingpushed into a retracted position as said frame is moved forwardly; aplurality of rearward pressure-applying means secured to and projectingrearwardly from said frame and adapted to move said frame forwardly; andmeans for energizing each of said rearward pressure-applying means i11-dependently of each other.

5. In a tunnel breastboard jumbo, the combination of a main frame,slidable in a horizontal fore-and-aft plane; a plurality of forwardlyprojecting hydraulic rams secured to the forward end of said frame, eachram having a housing enclosing and supporting the working end of itsassociated ram, and a second frame in which the housing is slidablysupported and to which the non-working end of each ram is connected;pressure-sensitive control means for separately energizing each of saidrams and for deenergizing each of said rams to a predetermined pressurewhen said main frame is being moved forward; rearwardly projectinghydraulic rams secured to said main frame; and control means forenergizing said rearwardly projecting rams to move said frame forwardwhile simultaneously forcing said forwardly projecting rams into aretracted position.

6. In a tunnel breastboard jumbo for supporting the core face, thecombination of a frame, slidable in a horizontal fore and aft plane; aplurality of forwardly projecting hydraulic rams secured to the forwardend of said frame; control means for separately energizing each of saidrams and moving it forward relative to said frame against the core face;control means permitting backward movement of said rams relative to saidframe while maintaining a predetermined pressure in each ram, to supportsaid core face when said frame is being moved forward; rearwardlyprojecting hydraulic rams secured to said frame; and control means forenergizing said rearwardly projecting rams to move said frame forwardwhile simultaneously forcing said forwardly projecting rams into theirretracted position without. loss of support for the core face.

7. In a tunnel breastboard jumbo, the combination of a movable frame; aplurality of forwardly projecting hydraulic rams secured to the forwardend of said frame; rearward-ly projecting hydraulic rams secured to saidframe; first pressure-sensitive control means for separately energizingeach of said forwardly projecting rams; second pressure-sensitivecontrol means energizing said rearwardly projecting rams at a greaterpressure than that to which said first means energize said forwardlyprojecting rams; and pressure-sensitive control means for relieving saidforwardly projecting rams of pressure exceeding a predetermined amount,so as to move said frame forward while simultaneously forcing saidforwardly projecting rams into a retracted position without decreasingtheir outward supporting thrust.

8. In a tunnel-digging support mechanism, the combination of a frameslidable in a horizontal plane; a plurality of forward pressure-applyingmeans, secured to and projecting forwardly from said frame;pressure-sensitive control means on said forward pressure-applying meansfor holding said forward pressure-applying means at a substantiallyuniform forward pressure while they are retracted relative to said frameas said frame is moved forwardly; a plurality of rearwardpressure-applying means secured to and projecting rearwardly from saidframe and adapted to move said frame forwardly; and

means for energizing said rearward pressure-applying means to a pressurelevel greater than the holding pressure of said forwardpressure-applying rams.

References Cited in the file of this patent UNITED STATES PATENTS724,666 Cooper Apr. 7, 1903 1,355,290 Updegrafif Oct. 12, 1920 FOREIGNPATENTS 12,575 Great Britain 1894 79,592 Germany Apr. 2, 1895 810,151Germany Aug. 6, 1951 658,998 Great Britain Oct. 17, 1951

